The invention relates to a method for producing a piston of an internal combustion engine that is designed as a finished, one-piece cooling channel piston with an upper part and a lower part supported by matching joining bosses that together form a joining zone and that are materially bonded by means of friction welding.
Friction welding is based on the principle by which sliding friction is generated between two components through relative movement and simultaneous pressure to create the required welding energy at the surfaces to be welded in the area of a joining zone. In known rotational friction welding machines, a motor-driven chuck and an upsetting device are used to provide the kinetic energy during the entire welding cycle. For friction welding, two work pieces are rubbed together under pressure and plasticized through the resulting frictional heat. Preferably the work piece installed in the driven chuck is rotated relative to the second work piece held stationary in the upsetting device. As soon as the temperature required for welding is reached, the upsetting device presses the two work pieces together. Disadvantageously, this method requires that one of the two components rotates at a high speed to provide the necessary energy.
A cooling channel piston is known from DE 10 2004 061 778 A1 consisting of an upper part and a lower part that are supported by way of matching joining bosses, both running rotationally symmetrically and spaced apart radially. A material bond is created between the inner joining bosses by means of friction welding in the area of a joining zone. The radially outer joining bosses are subsequently joined by means of a separate weld, where no provision is made for friction welding.
U.S. Pat. No. 6,155,157 shows a cooling channel piston with two components that can be produced separately and which are subsequently joined by a known friction welding procedure to form a material bond to create a one-piece cooling channel piston. This construction makes relatively simple piston production practicable, but in which the known piston concept regarding latitude in geometry, in particular in the design of joining bosses, is severely restricted.
Starting from the prior art, it would be desirable to improve the geometric design potential of pistons by means of an optimized joining technique for the purpose of achieving flexible piston production and a reduction in weight.